1. Field of Invention
The present invention is related to transmissive screens and rear projectors.
2. Description of Related Art
Rear projectors have progressively seen higher demand and been utilized more frequently as suitable displays for devices, such as home theater monitors and wide-screen television sets.
FIG. 10 illustrates the optical system of a rear projector. This rear projector 14 has a housing 50 including an optical projecting unit 20 for projecting an image, a light-guide mirror 30 for guiding the image projected by the optical projecting unit 20, and a transmissive screen 42 on which the image guided by the light-guide mirror 30 is projected.
This rear projector 14 particularly requires a transmissive screen 42 with wider viewing angle characteristics. Japanese Unexamined Patent Application Publication No. 2000-131506 (FIGS. 1 to 5) discloses such a transmissive screen with wider viewing angle characteristics. FIG. 11 is a sectional view of the transmissive screen. This transmissive screen 800 can include a Fresnel lens portion 810 can have Fresnel lens components on its light-exiting surface, a microlens array portion 820 disposed at the light-exiting surface side of the Fresnel lens portion 810 and having many microlenses 820a on its light-incident surface, a light shield portion 840 disposed at the light-exiting surface side of the microlens array portion 820, and a diffusing sheet 850 disposed at the light-exiting surface side of the light shield portion 840.
FIGS. 12 to 14 illustrate the structures of microlenses disclosed in Japanese Unexamined Patent Application Publication No. 2000-131506 (FIGS. 1 to 5). FIG. 12 shows rhombic microlenses, FIG. 13 shows a combination of rhombic microlenses and a hexagonal microlens, and FIG. 14 shows rectangular microlenses. In FIGS. 12 to 14, each (a) is a front view of the light-incident surfaces of these microlenses, while each (b) is a front view of the light-exiting surfaces of these microlenses; apertures 840a are arranged in the light shield portion 840, as shown in these drawings.
Japanese Unexamined Patent Application Publication No. 2001-133888 (FIGS. 3 and 4) also discloses such a transmissive screen with wider viewing angle characteristics. FIG. 15 is a perspective view of the transmissive screen. This transmissive screen 900 can have many spherical light-diffusing particles 920a arrayed vertically and horizontally. The light-diffusing particles 920a diffuse image light incident on the transmissive screen 900 to emit.
The above transmissive screens 800 and 900 have the advantage of better vertical viewing angle characteristics over known transmissive screens using lenticular lenses. This advantage is derived from the refraction of the microlenses 820a or the light-diffusing particles 920a. 
However, there is a need for a well-balanced increase in the vertical, horizontal, and oblique viewing angle characteristics in order to enhance the viewing angle characteristics for the above transmissive screens 800 and 900.